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# General algebra

### Factorisation

• The reverse process to expanding is called factorisation. In this case we are given an expression which is a sum of terms and we convert it to a product of two or more terms.
• Expressions may be factorised by removing factors common to two or more terms and then by grouping and if necessary regrouping.
$\ceqns && 3x+3x^2 \\ &=& 3\times x+2x\times x & \eqncomment{0.4}{where $$x$$ is the common factor} \\ &=& x(3+2x) \ceqne$
• Another example of factorising:
\begin{eqnarray}
2x^{3} +4x^{2}+6x = 2x(x^{2}+2x+3)
\end{eqnarray}
where $$2x$$ is the common factor.